MIDDLETOWN, Northern Ireland (CNN) -- Tucked away in the rolling hills of County Armagh in Northern Ireland lies a quiet village called Middletown. Its name couldn't be more apt. That's because Middletown stands amid a Brexit tug-of-war.
The reason can be found just yards outside of the village. Here, the Irish border separates Northern Ireland from the Irish Republic. For nearly a century, that boundary has shaped the village's history and its people.
During the decades-long sectarian conflict known as The Troubles, a huge British army barracks loomed over the area. Customs officials patrolled the border crossings.
A 1998 peace accord ended most of the bombings and kidnappings during a dark period of the country's history that was fueled by a split between unionists who wanted to stay in the United Kingdom and those in the Roman Catholic minority who favored a united Ireland.
With that agreement the barracks was torn down, replaced with a housing estate, and crossing the border became seamless.
Now, local residents fear another change -- a controlled border.
British Prime Minister Theresa May will travel to Brussels on Monday to meet with European leaders. This marks her deadline to settle three key points that need to be ironed out before Britain quits the European Union: Britain's financial settlement, the rights of EU citizens, and the Northern Irish border.
Britain has said it will leave both the single market and customs union when it leaves the bloc in March 2019 -- a move that critics say could lead to a so-called "hard border," with checkpoints -- something Ireland has indicated it doesn't want.
In August, a UK government paper said it favored a border without physical barriers and travel for UK and Irish citizens free of passport controls.
Finalizing the issue would allow Britain to proceed with talks on its future trading relations with the bloc. When border checks and blocks were removed 20 years ago, trade between the north and south improved. Today an estimated $1.5 billion dollars worth of business flows back and forth between Ireland and the UK each week.
Westminster and Brussels feel a long way from Middletown, but the consequences of discussions there could have a profound impact on residents.
Trevor Magill runs the post office in Middletown, and knows the importance of cross-border business.
"Sixty to 70% of my business comes from south of the border," he tells CNN. "So, it's the freedom of being able to move across that border freely that impacts on the level of business you are able to do."
One of the biggest employers in the region is the food company Linwoods Health Foods, which sells items like flaxseed and hemp protein worldwide, as well as bread and milk on both sides of the Irish border.
The milk comes from dairy farmers in Northern Ireland and the plastic containers come from a company in the Irish Republic. Linwoods vans cross the border dozens of times a day.
John Woods is the company's director, and has been working in the family-owned business for around 50 years. Re-establishing a border with checkpoints would require the business to make big changes.
"We would just have to abandon exports to the south on our dairy and our bakery side, and we would have to look at opening a health food factory in the south, as well," he says.
The border is a 310-mile meandering, invisible line that cuts through the lush, rolling slopes of the Irish countryside.
A few miles outside Middletown that line takes a peculiar twist. At Ward's Cross, cars motor on one side of the road in the Irish Republic, while cars on the other are travel in Northern Ireland.
The crossroads is named for the Ward family. One member of that clan, farmer Francie Ward, says renewed checkpoints could bring a slew of new problems.
"I have land on both sides," he tells CNN. "I don't know what will happen with Brexit."
Hundreds of small roads like Ward's Cross run across the border. During the decades of sectarian conflict many such routes were blocked, and some were blown up by the British army.
Some Northern Irish lawmakers are warning that a hard border could lead to a return of trouble.
May is scheduled to meet Monday with European leaders Jean-Claude Juncker and Donald Tusk. Tusk, the European Council president, has insisted that the Ireland border issue be resolved before any Brexit trade discussions can move forward.
Ireland says it is not trying to delay the Brexit process, but wants a detailed plan about how the border would operate.
Irish Foreign Minister Simon Coveney said Sunday that he was unsure if an agreement on the Northern Ireland border could be managed by Monday's deadline, but he said he hoped that May's meetings in Brussels might lead to agreement.
Woods of Linwoods worries more about the long-term economic impact.
"Our success of the peace process was not just the good work done by the peacemakers, but also by increasing employment. Lower unemployment pulls in people who might otherwise see themselves out of the system."
TM & © 2017 Cable News Network, Inc., a Time Warner Company. All rights reserved.